Android : Reduce Android volume press delay

I'd like to reduce volume button keypress delay on android devices. I have a Nexus 5 and tested that when i press on the screen, the response time is very smooth, but it's not for volume button keypress.

This is my code:

Button send;
send = (Button) findViewById(R.id.send);
send.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        text.setText("Hello world!");
    }
});

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if ((keyCode == KeyEvent.KEYCODE_VOLUME_DOWN)){
        text.setText("Hello world!)";
    }
    return true;
}

The delay between the hardware button press and the Button press on the touchscreen is about 0.2sec.

Is there a way to improve keypress response performance? My phone is rooted. Solutions for rooted devices accepted too.

Thank you